Fault Location on Telephone Cables

An improved approach to fault location by pulse echo ranging on unloaded telephone cables is proposed, which requires a knowledge of the output unit step transient response of a matched cable. This has been obtained by numerical integration for 19 AWG nonloaded telephone quadded toll cable. Experimental results are given for unloaded spiral-four cable which has similar properties. The output unit step response is also given for an idealized semiinfinite loaded line for which the attenuation is approximately constant and the phase shift is proportional to frequency up to the cutoff radian frequency, Ωc. This result is used to demonstrate that the optimum rectangular pulse, T1, for echo ranging on loaded lines is given by .